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Arrest of DNA replication of macrophages in BCG granuloma and peritoneal exudates by bacteria
H Kutsukake1, S Nagao, A Tanaka
1Department of Biochemistry, Shimane Medical University.
Abstract:
Previously we found that bacterial surface substances induced the suppression of DNA synthesis of macrophages. We examined in the present study whether DNA synthesis of macrophages could be similarly suppressed by whole bacteria themselves. For this purpose we isolated macrophages from BCG granuloma of guinea pigs and rats. The macrophages from both of the animals gave essentially the same results. No isolated macrophages containing bacilli were found to incorporate 3H-thymidine when tested by autoradiography. Further, DNA replication of peritoneal exudate macrophages was markedly and rapidly suppressed in vitro upon phagocytosis of various kinds of bacteria but not of non-bacterial preparations. A close correlation was found between granuloma formation and inhibition of 3H-thymidine incorporation by MDP, its analogs, and various bacteria. These findings suggest that macrophages suppress their DNA replication when they phagocytose bacteria and that they can discriminate between bacteria and non-bacterial preparations.
Insights
Macrophages suppress their DNA synthesis upon encountering whole bacteria, a process crucial for immune responses. This study confirms that macrophages can distinguish between bacterial and non-bacterial substances.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Bacterial surface substances are known to suppress macrophage DNA synthesis.
- The effect of whole bacteria on macrophage DNA synthesis requires further investigation.
Purpose of the Study:
- To determine if whole bacteria, similar to their surface substances, can suppress macrophage DNA synthesis.
- To investigate the mechanism of DNA synthesis suppression in macrophages upon phagocytosis of bacteria.
Main Methods:
- Isolation of macrophages from BCG granuloma in guinea pigs and rats.
- Autoradiography using 3H-thymidine to assess DNA synthesis in macrophages.
- In vitro phagocytosis assays with various bacteria and non-bacterial preparations.
Main Results:
- Macrophages from BCG granuloma showed suppressed DNA synthesis when containing bacilli.
- Peritoneal exudate macrophages exhibited rapid DNA replication suppression after phagocytosing bacteria in vitro.
- A correlation was observed between granuloma formation and 3H-thymidine incorporation inhibition.
Conclusions:
- Macrophages suppress their own DNA replication upon phagocytosing bacteria.
- Macrophages possess the ability to differentiate between bacterial and non-bacterial materials.
- This DNA synthesis suppression is linked to granuloma formation and immune response.